The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Modern wind turbines generally exist in two configurations: horizontal axis and vertical axis, the designations referring to the axis about which the turbine blade disk rotates. Horizontal axis wind turbine (HAWT) configurations are inherently more efficient than vertical axis wind turbines (VAWT) because the full blade disk faces the ambient wind, whereas the blades in a vertical axis turbine alternately advance into and retreat from the wind. Nonetheless, both configurations have certain recognized benefits and drawbacks. Commercial HAWTs are generally immense devices, mounted high in the air where they are exposed to higher wind velocities but where they contribute to visual pollution and interference with migratory and local bird flight and produce strobe-like effects during periods of low incident sunlight, i.e., dawn and dusk. On the other hand, VAWTs are generally installed closer to the ground. While this siting yields lower effective wind speeds, it effectively overcomes the visual pollution, bird and strobe effect problems of HAWTs. Being nearer the ground also allows VAWT's to be more readily repaired and maintained. Moreover, VAWTs can be placed in close proximity to each other, an attribute that is beneficial, especially for wind farm installations.
In both wind turbine types the ultimate objective is the maximization of the resultant power (the product of the shaft torque and the angular rate) delivered to an electrical generator for every ambient wind direction and velocity condition. As the foregoing summary highlights, it would be advantageous to develop wind turbines that have the inherent advantages of VAWTs that are also more efficient and thus competitive with HAWTs. The present invention is so directed.